1. Field of the Invention
The present invention relates to jet propulsion boats, and more specifically to a jet propulsion boat which generates a propulsion force by jetting water with power from an engine.
2. Description of the Related Art
JP-A 2008-291774 discloses a conventional example for this type of technique. JP-A 2008-291774 discloses a technique (a so called OTS system; Off Throttle Steering system) of differentiating two cases of turning and straight traveling from each other in a decelerated state and controls the engine output so as to keep thrust at a level such the boat can make a turn if it is determined that the boat is in a turning state. In particular, JP-A 2008-291774 discloses that the turning operation is assisted with a sustained engine output when the jet propulsion boat makes a turn while traveling at a slow speed.
Generally, in so called personal water crafts (PWCs), an upper limit value for the number of engine revolutions is set for a straight traveling pattern regardless of whether the craft is moving straight or turning. As a result, a PWC has a characteristic tendency that it has a large sideway thrust at the time of turning with a strong centrifugal force acting on the side of the PWC.
JP-A 2008-291774 discloses nothing about control techniques for making a turn while traveling at a high speed.